This invention relates to pigment compositions obtained by treating organic pigments with cyclic amidomethyl, thioamidomethyl, and amidinomethyl pigment derivatives that impart improved rheological properties and dispersibility.
Many types of organic pigments are known and each can be prepared by one or more known methods. Typically, however, the initially formed crude compounds are unsuitable for use as pigments and must undergo one or more additional finishing steps to modify the particle size, particle shape, or crystal structure to achieve suitable pigmentary quality, rheological properties, and dispersibility.
Methods to improve rheological properties are known. For example, pigments can be treated with various additives, such as sulfonic acid and sulfonamide derivatives of various pigments. E.g., U.S. Pat. Nos. 3,418,322, 3,446,641, 4,088,507, 4,310,359, and 5,368,641 and British Patents 1,544,839 and 2,009,205.
Other pigment derivatives have also been disclosed for use as pigment additives. For example, pyrazolylmethyl quinacridone derivatives are described in U.S. Pat. No. 5,334,727. Substituted benzamidomethyl quinacridones and structurally related phthalimidomethyl and sulfo-benzimidomethyl quinacridones are described in U.S. Pat. Nos. 3,635,981, 4,197,404, 4,256,507, 4,439,240, 4,455,173, 4,478,968, 4,541,872, 4,844,742, 4,895,949, 5,194,088, 5,264,032, 5,286,863, 5,424,429, 5,453,151, and 5,457,203. Analogous compounds in which a methylene bridging group is attached to a lactam ring nitrogen atom (i.e., (1-aza-2-oxocycloalkan-1-yl)methylquinacridones) are described in U.S. Pat. No. 5,207,829. These patents, however, do not disclose the cyclic amido methyl, thioamidomethyl, and amidinomethyl pigment derivatives of the present invention.
It has now surprisingly been found that pigment compositions having excellent pigmentary quality and rheological properties can be obtained by treating organic pigments with certain pigment derivatives bearing one or more cyclic amidomethyl, thioamidomethyl, or amidinomethyl substituents. Such advantages are found even in comparison to phthalimidomethyl quinacridones.